1. Field of the Invention
The present invention relates to alloys having excellent erosion resistance and suitable, for example, for use in instruments and parts such as erosion shields of turbines, valves, etc., which are susceptible to fluid erosion.
2. Description of the Prior Art
Stellites which are Co--Cr--W--C base alloys having very excellent erosion resistance and mechanical strength are now used as main materials for instruments and parts such as the erosion shields and valve seats of atomic power plants which are occasionally subject to erosion.
Stellites, however, contain a high percentage of cobalt and have caused troubles on radioactivity resulting from radioactivation of cobalt when the stellites are used for atomic power plants.
Japanese Laid-Open Patent No. 60865/1986 discloses cavitation-erosion resistant alloys comprising 10-30 wt.% of manganese, 10-30 wt.% of chromium, 0.5-3.0 wt.% of vanadium, not more than 0.3 wt.% of carbon, 0.2-1.0 wt.% of nitrogen and the balance essentially consisting of iron. However, according to the examination of the inventors, alloys having a high content of nitrogen such as those disclosed in Japanese Laid-Open Patent No. 60865/1986 result in too much stabilization of austenite. In addition, vanadium nitride is preferentially precipitated in the course of aging treatment and it becomes difficult to retain vanadium carbide which is effective for the enhancement of erosion resistance. As a result of above two reasons, good erosion resistance has not yet been obtained. That is, a high manganese-chromium-iron base alloy in combination with enhancement in the precipitation of vanadium carbide is the requirement for obtaining good erosion resistance.